Prince William and Catherine, Duchess of Cambridge have made a stunning appearance on the 'green carpet' at the first Earthshot Prize Awards.
They arrived at London's Alexandra Palace venue for the inaugural awards, which saw five out of 15 finalists awarded with a £1 million prize ($1.8 million AUD).
Each of the finalists was selected for their work towards creating new solutions to ongoing environmental issues, a cause close to the Duke and Duchess' hearts.
One Australian marine organisation called Living Seawalls made it into the top 15 finalists, but missed out on the five prizes.
But all eyes were on the royal couple as they arrived on Sunday night dressed in their finest.
Prince William donned black trousers, a black turtleneck and a dashing green velvet blazer in keeping with the evening's theme of environmentalism.
Meanwhile Duchess Catherine donned an elegant Alexander McQueen gown made from floating lilac chiffon, with a sparkling belt that drew attention to her slender waist.
The 39-year-old's outfit may not have been green in hue, but it was definitely a sustainable fashion choice.
Catherine's gown for the special event was actually a recycled frock and has been in her wardrobe for at least a decade now.
She was first photographed in the McQueen design in July 2011, when she attended the BAFTA Brits at the Belasco Theatre in Los Angeles, California.
She and William were newlyweds at the time and Catherine's flowing gown was a hit with royal fans from the US and back home in the UK.
Since then, the Duchess appears to have had a few alterations made, specifically swapping out the belt on the dress.
The original belt was a shimmering silver so light it almost appeared white, while the new belt has more of a gold tone, with a geometric design.
Her outfit was in keeping with a surprising dress code on the night, which instructed guests not to buy anything new to wear to the ceremony.
As such, it can be assumed that all of Catherine's accessories were also recycled from past events.
She kept her accessories minimal, styling the gown with a pair of large drop earrings set with what appear to be amethysts and emeralds.
She wore her hair long and loose, parting it deep to one side and styling the rest in soft, full curls over her left shoulder.
The Duke and Duchess of Cambridge weren't the only famous faces at the first Earthshot Prize Awards, with other UK celebrities making appearances on Sunday night.
The event featured performances by Ed Sheeran, Coldplay and Shawn Mendes, while film stars like Emma Watson – of Harry Potter fame – and Emma Thompson also attended.
The Prince of Wales voiced how proud he is of his son in a touching message just hours before the awards began.
"I am very proud of my son, William, for his growing commitment to the environment and the bold ambition of the Earthshot Prize," he wrote on social media alongside a photo of them hugging.
"As a world, we need to come together to inspire, reimagine and build the sustainable future we so desperately need.
"Over the coming decade, with future generations in mind, the Earthshot Prize, and its inspirational nominees, will help us find the innovative solutions."